In general, permanent waving of human hair is achieved by chemically breaking the sulfur to sulfur or disulfide cystine bonds occurring naturally in human hair and then reforming the cystine bonds while the hair is wrapped or curled on rods. The sulfur to sulfur cystine bonds in human hair maintain the hair in a naturally straight or curly configuration and, in order to permanently reshape the hair into a lasting, different configuration, a significant percentage of the sulfur to sulfur bonds must be broken and then reestablished after the hair is reconfigured in a desired position, such as wrapped around a suitable mandrel or roller. In general, the sulfur to sulfur cystine bonds are broken with a composition containing a reducing agent and after the hair is wound onto a curl formation around a rod or roller, the sulfur to sulfur cystine bonds are relinked or reestablished while the hair is in the curl formation by contacting the hair in the new formation with an oxidizing agent, such as hydrogen peroxide or a water-soluble bromate.
There are three general types of permanent wave compositions or lotions used to break the cystine bonds in human hair, generally known as acid wave compositions; alkaline wave compositions; and neutral wave compositions. Of these three, the acid and alkaline wave compositions are most significant commercially. Permanent wave compositions containing an alkaline salt of thioglycolic acid (TG), such as ammonium thioglycolate as the reduction agent, are generally known as alkaline wave compositions and generally have a pH in the range of about 7.5 to about 9.4. The alkaline wave compositions are known as the conventional cold wave compositions, since free alkali penetrates and swells the hair shaft allowing the reducing agent to enter the hair shaft and break the sulfur to sulfur bonds without added heat. The permanent wave compositions containing glycerol monothioglycolate (GMTG) are known as acid wave compositions even though the pH of these compositions can be as high as about 9.0. Generally speaking, the acid permanent wave compositions have a lower pH than the alkaline permanent wave compositions and, therefore, require heat and/or longer processing time to achieve sufficient reaction of the reducing agent. The alkaline permanent wave compositions produce a stronger, longer lasting curl while the acid permanent wave compositions provide a softer feel but a less distinct curl pattern of shorter curl duration.
The reducing agents most commonly used in cold waving hair lotions for rupturing cystine linkages are thiols or mercaptans as well as sulfites and/or bisulfites. A number of mercaptans can only provide acceptable efficiency at high pH whereas others with a lower pK and a high ionization constant can be effective at lower pH levels. For example, the ammonium salt of thioglycolic acid can provide acceptable waving efficiency (reduction) if the pH of the solution exceeds 9. Other compounds such as thioglycolamides or glycol thioglycolates, sulfites and/or bisulfites can be used at neutral or even slightly acidic pH. The following are mercaptans and thiois which have commonly been used in cold waving lotions: thioglycolic acid, thiolactic acid, cysteine, thioglycerol, thioglycolic hydrazide, thioglycolamide, glycerol monothioglycolate, beta-mercapto-propionic acid, N-hydroxyethyl mercaptoacetamide, N-methyl mercapto-acetamide, beta-mercaptoethylamine, beta-mercapto-propionamide, 1-mercaptoethanesulfonic acid, dimercapto-adipic acid, dithiothreitol, homocysteinethiolactone, cysteine derivatives, and polythiol derivatives formed by the addition of cysteamine onto a maleic anydride-alkylvinylether copolymer. The sulfites and/or bisulfites most commonly used are the sodium and ammonium salts. The amount of the reducing agent used is that sufficient to rupture a sufficient number of disulfide bonds for effective hair waving or hair straightening as would be appreciated by one of ordinary skill in the art, for example about 0.1% to about 22% by weight of the composition, preferably about 1.0% to about 22% by weight.
The reducing action of mercaptans on keratin is due mostly to the dissociated form of the thiol groups, the thiolate anion. Acid permanent waves sufficiently curl hair at a lower pH compared to alkaline permanents because the waving agents in these permanents have low pKa values and thus exist predominantly in dissociated (thiolate anion) form at a pH near neutral, or slightly acidic pH. Hence, the pKa value shows that some mercaptans are efficient at high pH while others with a low pKa value and high ionization constant are efficient at lower pH values. For example, it is well known that the alkaline salts of thioglycolic acid, e.g., the ammonium salt of thioglycolic acid (pKa=10.4) has acceptable waving efficiency only if the pH of solution exceeds 9, see Zviak, Charles, The Science of Hair Care, Permanent Waving and Hair Straightening, p. 191, 1986; while amides such as thioglycolamide (pKa=8.4), and esters such as glycerol thioglycolate (pKa=7.8) give acceptable waving efficiency at neutral and even slightly acid pH.
The cysteinamide reducing agent of the composition and method of the present invention is unexpectedly effective in the pH range of about 7.5 to about 9.5 and particularly in the pH range of about 8.0 to about 9.2.
Different reducing agents are effective to break the cystine bonds that cross-link human hair protein at different pHs. Generally speaking, the acid permanent wave compositions having a lower pH include reducing agents such as bisulfites, e.g., ammonium bisulfite, or glycerol monothioglycolate, capable of breaking the sulfur to sulfur cystine bonds within lower pH ranges, whereas the alkaline permanent wave compositions, having pH's in the range of about 7.5 to 9.5, require an alkaline salt of thioglycolic acid or an alkaline salt of a dithioglycolic acid - so that the alkali can penetrate and swell the hair shaft for easier penetration of the reducing agent in order to break the sulfur to sulfur cystine bonds.
When the reducing agent is a salt of thioglycolic acid, such as ammonium thioglycolate, the reducing agent breaks the sulfur to sulfur cystine hair bonds best under high pH conditions (above 9.0) and therefore is included in a lotion in an amount sufficient to provide enough free alkali in solution for a composition pH of about 7.5 to 9.5. Alternatively, the high pH can be provided with a different alkali in the reducing agent composition, such a monoethanolamine, disopropanolamine or metal hydroxides. The lotion can be buffered, such as with ammonium bicarbonate or other known buffers, to maintain a suitable pH.
The use of diammonium dithiodiglycolate in acid or alkaline permanent wave lotions allows greater flexibility in processing time because it minimizes the possibility of overprocessing. This is due to the fact that the reaction of thioglycolic acid (TGA) with hair keratin is an equilibrium process. Thus by including diammonium dithiodiglycolate (oxidized TGA) in the wave lotion, the rate of the reaction of the thioglycolic acid with hair keratin is decreased and prevented from going to completion.
Generally, the permanent wave compositions of the prior art do not include moisturizers, such as glycerine, since moisturizers cause loss of curl, as disclosed in Cannell et al. U.S. Pat. No. 4,301,820.
One of the biggest problems associated with the permanent waving process is due to human error in the person applying the permanent waving lotion. If the reducing agent is applied to the hair shaft for the wrong period of time, too many or too few of the sulfur to sulfur bonds in the hair shaft are broken, resulting in seriously damaged hair or resulting in hair which has not been sufficiently treated to achieve a permanent wave with long lasting potential. Some of the reasons that the person applying the permanent wave composition has difficulty in determining the correct amount of time for processing is that the reducing agent reaction in breaking the sulfur to sulfur bonds is dependent upon the amount of heat applied to the hair; the amount of time the reducing agent is in contact with the hair; the concentration of reducing agent; the pH of the lotion applied; and the condition of hair.
Perhaps the most difficult factor for the applier of the permanent wave lotion to assess in determining how long to apply the reducing agent to the hair is the condition of the hair at the time of the permanent wave. It is well documented in the literature and prior art that the hair can be damaged by abuse of chemicals, e.g., by shampooing, permanent waving, tinting, frosting, bleaching, and particularly any hair treatment involving the use of hydrogen peroxide; mechanical treatment, e.g., thermal appliances; and environmental conditions, e.g., climate and pollution. It is well known that damaged hair, depending upon the stage and degree of damage of the hair, has significantly different chemical activity to reducing agents than normal or undamaged hair. If too many or the sulfur to sulfur bonds in the hair are broken by the reducing agent, the hair will be seriously weakened and may disintegrate.
It is theorized that somewhere in the range of about 20% to about 60% of the natural sulfur to sulfur cystine bonds in the hair shafts should be broken in order to give the hair the capability of being reshaped to any desired shape, such as curled around a rod or roller, and capable of retaining this shape. If too few of the sulfur to sulfur bonds are broken, the natural or normal configuration of the hair will predominate, causing the hair to retain its previous shape. This is because the predominant, prior or natural, bonds in the hair dictate that the hair will remain in the old configuration or shape. Hydrogen bonds are physically broken when wet hair is stretched and wrapped around a roller. When the hair is dried, the hydrogen bonds are reformed in a curled position or shape. While the hydrogen bonds aid to maintain the hair in the new configuration, the sulfur to sulfur cystine bonds are much stronger and, to a much greater extent than the hydrogen bonds, control the efficacy of the permanent wave.
In order to successfully provide a satisfactory permanent wave in the hair, the sulfur to sulfur cystine bonds reformed in the hair in the new or curled configuration, when the hair is later oxidized with the neutralizing agent, should be stronger than the prior or natural cystine hair bonds. It is desired, therefore, when permanent waving, that enough new bonds in a new hair configuration are formed during permanent waving to outweigh the number of old bonds remaining that tend to form the hair in its prior of natural configuration, whether it be straight or naturally curled.
Since damaged hair already has a significant number of the sulfur to sulfur cystine bonds broken due to some chemical, mechanical or environmental abuse, particularly the chemical abuses, such as bleaching, tinting or frosting, it is difficult to determine what length of time, and what reducing agent concentration to apply to the hair to provide the hair with the proper number of sulfur to sulfur bonds remaining after the reducing agent treatment. Significantly damaged hair, such as tinted hair, may require a reducing agent lotion application for a period of only about 5 minutes whereas a normal hair, not significantly damaged, may require the reducing agent lotion for a period of approximately 20 minutes under the same reducing agent concentration and temperature in order to result in both the damaged and normal hair having approximately the same curl configuration. Ideally, after the reducing agent treatment, every one of the hair shafts treated will contain the same ratio of broken to unbroken bonds so that this same ratio can be re-established in each hair shaft when the hair is in the new configuration to provide a consistent strong curl over the entire head of hair.
Generally, the reducing agent lotion is applied to the hair by first shampooing the hair and then applying the reducing agent lotion to the hair, either before or after the hair is wrapped around suitable rollers. Since it is not possible for even the experienced permanent wave applier to accurately determine visually the extent of damage to the hair in order to have a better idea of how long the reducing agent should be in contact with the hair, it is necessary to take a "test curl" so that after a predetermined amount of time, for example 10 minutes, a first roller is removed from the hair and the curl is felt and stretched in an attempt to determine if the curl formation is strong enough. Once it is determined that the reducing agent has been in contact with the hair for a sufficient time period, the hair is rinsed thoroughly with water while still on the rollers or rods and, while the hair remains on the rollers or rods, a neutralizing agent is applied to oxidize and reform the sulfur to sulfur bonds while the hair is in the new, rolled configuration. The neutralizing agent contains an oxidizing agent, such as hydrogen peroxide or a bromate salt, in order to reestablish the sulfur to sulfur bonds to leave the hair in a relatively permanent, e g., 2-4 months, new configuration. The rods are removed, before or after rinsing out the neutralizing agent.
When the reducing agent lotion is applied to sections of the head prior to rolling that portion of the hair onto the rods it is called a lotion wrap whereas when the hair is rolled on the rods or rollers first and then the lotion applied onto all of the hair after rolling, this is called a water wrap. The timing for the reducing agent to be in contact with the hair for a lotion wrap is begun from the time that all rods are on the head, and the timing for a water wrap begins from the time that the lotion application is completed. The capability of using a water wrap is clearly more desirable since the lotion is applied to the entire head of hair all at once in a short period of time and can be rinsed from the hair all at once to provide a more uniform reducing agent contact time for all of the hair.
Prior art patents directed to permanent waving compositions intended to permanently wave both normal and damaged hair are found in the Klemm et al U.S. Pat. No. 4,273,143; and Cannell et al U.S. Pat. No. 4,301,820. Japanese Patent No. 57-212110 appears to be directed to a post-permanent treatment containing glycerine to give hair sheen and luster.
In accordance with the present invention, a new cysteinamide reducing agent has been found for breaking sulfur to sulfur cystine bonds in hair that is unexpectedly effective as a reducing agent to break cystine hair bonds in the permanent waving process and can provide set retention benefits and other bodifying advantages in hair sprays, styling aids, mousse compositions, shampoos, conditioners, conditioning shampoos, hair bodifying compositions, and hair straightening compositions. In accordance with one important embodiment of the present invention, the cysteinamide reducing agent is included in an alkaline permanent wave composition in a single formula that can be applied in a single predetermined amount of time to the hair, regardless of the structure of the hair, whether it be damaged or not, and this compositions is capable of being water wrapped without the use of a dryer, hair caps or other heat treatment to speed the reducing agent reaction. The composition of the present invention produces a strong curl like an alkaline wave composition yet leaves the hair feeling soft like an acid wave composition.